The sticky traps attract the inch-long emerald ash borer, which has wiped out 30 million ash trees in Michigan and was first found in Pennsylvania last year in Cranberry Twp. The trap survey is paid for with a $2.5 million federal grant.

“The beetles start to fly in May, so that’s why the traps are being set out,” said Scott Simpson, district manager of Davey Tree & Lawn Care’s Gibsonia office. “They will be moving and they will be expanding their area from Cranberry and Marshall Township, but how far they’ll go is the question.”

The state Department of Agriculture will hold off on making any sweeping decisions on treating or removing ash trees until after the purple traps show how far Western Pennsylvania’s infestation has spread, spokeswoman Jean Kummer said.

“We just don’t know how bad we have it yet,” she said.